VIT Engineering VIT Engineering Solved Paper-2009

  • question_answer
    A piece of metal weighs \[45g\] in air and \[25g\] in a liquid of density \[1.5\times {{10}^{3}}kg-{{m}^{-3}}\] kept at \[30{}^\circ C\]. When the temperature of the liquid is raised to \[40{}^\circ C\], the metal piece weighs \[27g\]. The density of liquid at \[40{}^\circ C\] is \[1.25\times {{10}^{3}}kg-{{m}^{-3}}\]. The coefficient of linear expansion of metal is

    A)  \[1.3\times {{10}^{-3}}{{/}^{\text{o}}}C~\]

    B)  \[5.2\times {{10}^{-3}}{{/}^{\text{o}}}C\]

    C)  \[2.6\times {{10}^{-3}}{{/}^{\text{o}}}C\]

    D)  \[0.26\times {{10}^{-3}}{{/}^{\text{o}}}C\]  

    Correct Answer: C

    Solution :

    The volume of the metal at \[{{30}^{o}}C\]is \[{{V}_{30}}=\frac{loss\,of\,weight}{specific\,gravity\,\times g}\] \[=\frac{(45-25)g}{1.5\times g}=13.33c{{m}^{3}}\] Similarly, volume of metal at \[{{40}^{o}}C\]is \[{{V}_{40}}=\frac{(45-27)g}{1.25\times g}=14.40c{{m}^{3}}\] Now, \[{{V}_{40}}={{V}_{30}}[1+\gamma ({{t}_{2}}-{{t}_{1}})]\] or \[\gamma =\frac{{{V}_{40}}-{{V}_{30}}}{{{V}_{30}}({{t}_{2}}-{{t}_{1}})}\] \[=\frac{14.40-13.33}{13.33(40-30)}\] \[=8.03\times {{10}^{-3}}{{/}^{o}}C\] \[\therefore \] Coefficient of linear expansion of the metal is \[\alpha =\frac{\gamma }{3}=\frac{8.03\times {{10}^{-3}}}{3}\] \[\approx 2.6\times {{10}^{-3}}{{/}^{o}}C\]


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